Reduction, ontology and the limits of convention

It is widely agreed that ontological reduction is possible, that the ontology of one theory can be shown to be nothing over and above the ontology of a distinct theory. However, it is also widely agreed that one assesses a theory’s ontology by determining what it says there is. I show that there is a tension between these orthodox positions. To resolve this tension, I propose and defend the view that the ontological commitments of a statement are sensitive to the theory in which it is embedded.